JP2020128322A - Glass and method for producing the same and glass light guide plate - Google Patents

Abstract

To provide a glass showing excellent weather resistance over the long term.SOLUTION: A glass 10A has, on the surface of at least one principal face 21, an alkaline earth metal depletion layer 30 wherein, in the area within 5 nm from the surface in depth, each content of alkaline earth metal elements by XPS measurement is 1 mass% or less, the glass having the following composition: in terms of mass percentage on an oxide basis, SiOof 60-85%, AlOof 0-10%, MgO of 0-10%, CaO of 0-20%, SrO of 0-15%, BaO of 0-15%, NaO of 2-20%, KO of 0-10%, BOof 0-20%.SELECTED DRAWING: Figure 1

Description

The present invention relates to glass, a method for manufacturing the same, and a glass light guide plate. The glass of the present invention is preferably used as a glass light guide plate for an edge light type planar light emitting device.

Conventionally, a light guide plate made of a resin material has been widely used as a light guide plate of an edge light type planar lighting device (see Patent Document 1). However, the light guide plate made of a resin material has low heat resistance and large thermal expansion. Therefore, when the light guide plate made of a resin material is exposed to a high temperature and high humidity environment especially during long-term use, deterioration or deformation of the light guide plate made of a resin material causes deterioration of the device. And there was a problem of poor brightness

Therefore, use of a glass plate as a light guide plate has been studied as a material having higher heat resistance and less thermal expansion than a light guide plate made of a resin material (see Patent Document 2). The conventional glass light guide plate has a problem of weather resistance. Specifically, when placed under high temperature and high humidity for a long time, the surface of the glass light guide plate looks white and cloudy due to the reaction product of the reaction between the soluble component and the water in the glass. White haze occurs. Then, there is a problem that due to the cloudiness of white, the brightness reduction and the brightness unevenness of the planar lighting device using the glass light guide plate occur.

Conventionally, as a method for improving the weather resistance of glass, a method of coating the glass surface with powder, a chemical solution or the like has been generally used. Further, as another means for enhancing the weather resistance of glass, in the glass manufacturing process, a process of spraying SO ₂ or SO ₃ gas onto the surface of the glass plate (dealkalation treatment) is used to remove the alkali component and SO ₂ contained in the glass. Alternatively, it has been proposed to react with SO ₃ to form a dealkalized layer.

For example, in US Pat. No. 6,037,839, in the manufacture of float glass in which a glass ribbon is drawn across a molten metal surface, the top surface of the float glass is exposed to an amount of SO ₃ effective to reduce contamination of the top surface of the float glass. A method of reducing the contamination of the upper surface of the float glass is disclosed.

JP, 2014-67525, A JP, 2009-199875, A International Publication No. 2014/148046

However, the conventional method of improving the weather resistance of glass is that the light extraction efficiency is impaired due to the change in the optical properties of the glass surface, that it is difficult to maintain the weather resistance for a long time, and it is very high. Since it has an internal transmittance, it is difficult to apply it to a light guide plate in that the brightness is affected even with an extremely thin cloudiness.

Further, in the method of increasing the weather resistance of the glass by dealkalization treatment, although it is possible to improve the temporary weather resistance, alkaline earth metal present on the glass surface, alkali metal reacts with the organic matter attached to the glass surface, to remove salts. The formation causes cloudiness. Therefore, it is not possible to construct a glass surface that can maintain excellent weather resistance for a long period of time by the conventional method of dealkalizing treatment.

Therefore, it is an object of the present invention to provide a glass exhibiting excellent weather resistance for a long period of time, a method for producing the same, and a glass light guide plate.

The present inventors have found that the above problems can be solved by setting the content of each alkaline earth metal element in the outermost surface region of the glass to a specific amount or less, and have completed the present invention.

That is, in the present invention, in at least one of the main surfaces, the content of each alkaline earth metal element in the region within a depth of 5 nm from the surface layer by XPS measurement is 1% by mass or less, and the glass having the following composition I will provide a.
The oxide-based mass percentage display is 60 to 85% SiO ₂ , 0 to 10% Al ₂ O ₃ , 0 to 10% MgO, 0 to 20% CaO, 0 to 15% SrO, and BaO. Composition containing 0 to 15%, ₂ to 20% Na ₂ O, 0 to 10% K ₂ O, and 0 to 20% B ₂ O _3.

The present invention also provides a method for producing glass, which comprises a step of subjecting at least one main surface of glass having the following composition to a dealkalizing earth metal treatment with an acid gas or an acid solution.
By mass percentage based on oxides, _{SiO 2 60~85%, Al 2 O} 3 0-10% of MgO 0-10%, 0 to 20% of CaO, 0 to 15% of SrO, BaO, Composition containing 0 to 15%, ₂ to 20% Na ₂ O, 0 to 10% K ₂ O, and 0 to 20% B ₂ O _3.

The glass of the present invention has a specific composition, and by setting each content of the alkaline earth metal elements in the region of the outermost surface of the glass to be a specific amount or less, the alkaline earth metal component on the glass surface, and the alkali metal component Can be suppressed from reacting with components such as organic substances. Therefore, in the glass of the present invention, the occurrence of cloudiness on the surface of the glass is suppressed even when the glass of the present invention is left under high temperature and high humidity for a long time. By using the glass of the present invention as the light guide plate, it is possible to suppress the decrease in brightness and the occurrence of uneven brightness in the planar lighting device.

FIG. 1 is a schematic cross-sectional view showing one structural example of the glass light guide plate of the present invention. FIG. 2 is a schematic cross-sectional view showing another configuration example of the glass light guide plate of the present invention. FIG. 3 is a graph showing a profile obtained by XPS measurement in Example 1. FIG. 4 is a graph showing a profile obtained by XPS measurement according to an embodiment of the present invention. FIG. 5 is a profile obtained by XPS measurement according to an embodiment of the present invention. FIG. 6 is a graph showing a profile obtained by XPS measurement in Comparative Example 1. FIG. 7 is a graph showing a profile obtained by XPS measurement in Comparative Example 2. FIG. 8 is a graph showing a profile by XPS measurement of the total content of alkaline earth metals in Example 1. FIG. 9 is a graph showing a profile by XPS measurement of the total content of alkaline earth metals in one embodiment of the present invention. FIG. 10 is a graph showing a profile by XPS measurement of the total content of alkaline earth metals in one embodiment of the present invention. FIG. 11 is a graph showing a profile by XPS measurement of the total content of alkaline earth metals in Comparative Example 1.

[Glass]
In the glass of the present invention, in at least one main surface, each content of alkaline earth metal elements in a region within a depth of 5 nm from the surface layer by XPS measurement is 1 mass% or less, preferably 0.9 mass. % Or less, and more preferably 0.8% by mass or less. In the present invention, “alkaline earth metal element” refers to Ba, Ca and Sr.

In the present invention, "the content of each alkaline earth metal element in the region within a depth of 5 nm from the surface layer by XPS measurement is 1% by mass or less" means that in the entire region within a depth of 5 nm from the surface layer, The content of each alkaline earth metal element measured by XPS is 1% by mass or less. Hereinafter, a region having a depth of 5 nm or less from the surface layer in which each content of each alkaline earth metal element measured by XPS is 1% by mass or less is also referred to as “alkaline earth metal deficient layer”.

As one aspect of the glass of the present invention, for example, on at least one of the main surfaces, a glass in which each content of Ba, Ca, and Sr by XPS measurement in a region within a depth of 5 nm from the surface layer is 1% by mass or less Can be mentioned.

The glass of the present invention adheres to the glass surface because the content of each alkaline earth metal element in the region within a depth of 5 nm from the surface layer by XPS measurement is 1% by mass or less on at least one main surface. It is possible to suppress the formation of salts by preventing the organic substances and the like from reacting with the alkaline earth metal component on the glass surface under high temperature and high humidity to prevent clouding.

The cause of the organic substances adhering to the glass surface is, for example, volatile matter from the ink applied to the surface of the glass for the purpose of forming a light scattering portion, and reflection in the vicinity of the glass light guide plate in the glass surface illumination device. Examples thereof include volatile substances from the sheet or the scattering sheet, or residues of the protective film attached to the glass light guide plate before use.

In the glass of the present invention, each content of the alkaline earth metal element in a region within a depth of 10 nm from the surface layer by XPS measurement is preferably 4% by mass or less, and more preferably at least on one main surface. It is 3.5 mass% or less, and more preferably 3 mass% or less.

In the glass of the present invention, each content of the alkaline earth metal elements in a region within a depth of 15 nm from the surface layer by XPS measurement is preferably 5.5 mass% or less on at least one main surface, and It is preferably 5.3 mass% or less, and more preferably 5 mass% or less.

As one aspect of the glass of the present invention, for example, glass in which each content of Ba, Ca, and Sr by XPS measurement in a region within a depth of 10 nm from the surface layer is 4 mass% or less, and within a depth of 15 nm from the surface layer A glass in which each content of Ba, Ca, and Sr by the XPS measurement in the region is 5.5 mass% or less is mentioned.

As one aspect of the glass of the present invention, it is preferable that the total content of alkaline earth metal elements at a depth of 5 nm from the surface layer measured by XPS is 3% by mass or less, and more preferably at least on one main surface. It is 2.5 mass% or less, and more preferably 2 mass% or less.

As one aspect of the glass of the present invention, the total content of alkaline earth metal elements at a depth of 10 nm from the surface layer measured by XPS is preferably 4.5% by mass or less on at least one main surface, and It is preferably 4% by mass or less, and more preferably 3.5% by mass or less.

As one aspect of the glass of the present invention, the total content of alkaline earth metal elements at a depth of 15 nm from the surface layer measured by XPS is preferably 6% by mass or less, and more preferably at least one main surface. It is 5.5 mass% or less, more preferably 5 mass% or less.

Examples of profiles obtained by XPS measurement in one embodiment of the glass of the present invention are shown in FIGS. 8 to 10 show profiles of the total content of alkaline earth metal elements in one embodiment of the glass of the present invention measured by XPS.

The content of the alkaline earth metal element can be confirmed by XPS measurement. The XPS measurement referred to in the present invention is performed under the following measurement conditions.

(XPS measurement conditions)
The depth direction distribution of each element concentration in the glass substrate after cleaning is measured by X-ray photoelectron spectroscopy (hereinafter referred to as XPS) using C60 ion sputtering. For the measurement, ESCA5500 manufactured by ULVAC-PHI, Inc. was used, and Si(2p), Al(2p), Na(2s), Ca(2s), Sr(3p3), Ba(3d5), O(1s) were used. Using the peak, measurement is performed under the conditions of a pass energy of 117.4 eV, an energy step of 0.5 eV/step, and a detection angle (angle between the sample surface and the detector) of 75°. Analysis software MultiPak is used for spectrum analysis. The Shirley method is applied to subtract the background of the spectrum.

The glass according to the present invention has the composition described below. More specifically, the glass according to the present invention has the composition described below in the glass portion excluding the alkaline earth metal deficient layer.

The effects of the present invention include, as described above, having an alkaline earth metal deficient layer suppresses the reaction of alkaline earth metal components with components such as organic substances on the glass surface. The alkaline earth metal deficient layer can be easily formed by glass having the following composition. In other words, it is extremely difficult or impossible to achieve an alkaline earth metal deficient layer in a glass having a composition that does not have the following composition, even if an attempt is made to form an alkaline earth metal deficient layer.

The reason for adding each component in the composition will be described below.
The composition of the glass according to the present invention is a mass percentage display on an oxide basis, SiO ₂ is 60 to 85%, Al ₂ O ₃ is 0 to 10%, MgO is 0 to 10%, CaO is 0 to 20%, It contains 0 to 15% SrO, 0 to 15% BaO, ₂ to 20% Na ₂ O, 0 to 10% K ₂ O, and 0 to 20% B ₂ O ₃ .

SiO ₂ is the main component of glass. The content of SiO ₂ is preferably 60% or more, more preferably 62% or more, still more preferably 63% or more in order to maintain the weather resistance and devitrification property of glass. On the other hand, the content of SiO ₂ is preferably 85% or less, more preferably 80% or less, further preferably 72% or less, and particularly preferably from the viewpoint of facilitating the dissolution and improving the foam quality. It is 68% or less.

When the content of Al ₂ O ₃ is large, the viscosity at the time of dissolution is increased, and bubbles may be hard to escape. Therefore, the content of Al ₂ O ₃ is preferably 10% or less, more preferably 9% or less, further preferably 8% or less, and particularly preferably 6% or less.

When Al ₂ O ₃ is contained, the content of Al ₂ O ₃ is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 2.5% or more. is there. Al ₂ O ₃ has the effect of reducing non-crosslinking oxygen in the glass, and thus contributes to improving the weather resistance of the glass.

MgO has the effect of lowering the viscosity during glass melting and promoting melting. Also, it may be contained because it has the effect of reducing the specific gravity and making it difficult for the glass to be scratched. When MgO is contained, its content is preferably 0.1% or more, more preferably 0.5% or more, still more preferably 2% or more.

On the other hand, if MgO is contained, the coefficient of thermal expansion of the glass increases, and the devitrification property may deteriorate. Therefore, the content of MgO is preferably 10% or less, more preferably 8% or less, further preferably 5% or less, and particularly preferably 3% or less.

CaO is a component that accelerates melting of the glass raw material and adjusts viscosity, thermal expansion and the like, and may be contained in order to obtain such an effect. When CaO is contained, its content is preferably 1% or more, more preferably 3% or more, still more preferably 5% or more. Further, in order not to deteriorate the devitrification property of the glass, it is preferably 20% or less, more preferably 15% or less, still more preferably 12% or less.

The composition may include SrO and BaO. Similar to MgO and CaO, these components are components useful for promoting melting of the glass raw material and adjusting thermal expansion, viscosity and the like. It is also a useful component for increasing the refractive index of glass.

SrO has the effect of increasing the coefficient of thermal expansion and reducing the high temperature viscosity of glass. SrO may be contained in order to obtain such an effect. When SrO is contained, its content is preferably 1% or more, more preferably 2% or more. However, the content of SrO is preferably 15% or less, more preferably 12% or less, further preferably 8% or less, and particularly preferably 5% or less in order to suppress the thermal expansion coefficient of the glass to be low and not to deteriorate the weather resistance. Is.

BaO has the effect of increasing the coefficient of thermal expansion and lowering the high temperature viscosity of glass, like SrO. BaO may be contained to obtain the above effects. When BaO is contained, its content is preferably 2% or more, more preferably 4% or more, and further preferably 6% or more. However, the content of BaO is preferably 15% or less, more preferably 12% or less, still more preferably 10% or less, particularly preferably 8% or less so that the thermal expansion coefficient of the glass is suppressed to be low and the weather resistance is not deteriorated. Is.

Alkali metal oxides such as Na ₂ O and K ₂ O are components useful for promoting melting of the glass raw material and adjusting thermal expansion or viscosity. The total content of these components is preferably 2% or more, more preferably 5% or more, and particularly preferably 10% or more. Further, in order to keep the coefficient of thermal expansion low and to improve the devitrification property, it is preferably 25% or less, more preferably 20% or less.

The content of Na ₂ O is preferably 2% or more, more preferably 5% or more, further preferably 8% or more, particularly preferably 10% or more. However, the content of Na ₂ O is preferably 20% or less, and more preferably 15% or less in order to maintain the clarity during melting and maintain the foam quality of the glass produced.

K ₂ O is a component that contributes to weather resistance, but in order to maintain the devitrification property of glass, the content of K ₂ O is preferably 10% or less, more preferably 5% or less, and further preferably 2% or less. And may not be included.

B ₂ O ₃ may be contained because it is a useful component for promoting melting of the glass raw material, improving mechanical properties and weather resistance, and lowering the refractive index of glass. The content is preferably 1% or more, more preferably 2% or more, still more preferably 3% or more. On the other hand, in the case of soda lime silicate glass, the content is preferably 20% or less, more preferably 15% or less, in order to prevent inconveniences such as the formation of striae due to volatilization and the erosion of the furnace wall. It is preferably 10% or less, particularly preferably 5% or less, and most preferably substantially not contained.

The composition of the glass according to the present invention can be measured by the fluorescent X-ray method. Further, boron B, which is a light element and difficult to measure by the fluorescent X-ray method, and trace elements of 1000 mass ppm or less can be measured by the ICP emission spectroscopy.

The glass according to the present invention preferably contains 5 to 100 mass ppm of iron oxide in terms of Fe ₂ O ₃ . To contain 5 to 100 mass ppm of iron oxide in terms of Fe ₂ O ₃ means that the total amount of iron oxide converted to Fe ₂ O ₃ is 5 to 100 mass ppm. The total amount of iron oxide is the total content of Fe ²⁺ (divalent iron) and Fe ³⁺ (trivalent iron) present in the glass.

Iron oxide is a useful component for improving the solubility of glass raw materials. However, since iron oxide has absorption in the visible light region, when the iron oxide content increases, the transparency of glass in the visible light region decreases. When the iron oxide content is in the above range, a highly transparent glass having a low absorption coefficient in the entire visible light wavelength range (380 to 780 nm) is obtained.

When the iron oxide content is 5 mass ppm or more in terms of Fe ₂ O ₃ , the infrared absorption of the glass becomes appropriate, so that the solubility can be improved, and the cost for refining the raw material is very high. There is no possibility of this. If the iron oxide content is 100 mass ppm or less in terms of Fe ₂ O ₃ , there is no risk of impairing the glass transparency in the visible light range.

The iron oxide content is preferably 50 mass ppm or less in terms of Fe ₂ O ₃ , more preferably 25 mass ppm or less, further preferably 20 mass ppm or less, and 15 mass ppm or less. Is particularly preferable. The iron oxide content can be adjusted by the amount of iron added during glass production.

The glass of the present invention preferably has a Fe ²⁺ content (hereinafter, also referred to as the amount of divalent iron) of 0 to 50 mass ppm. When the amount of divalent iron is 50 mass ppm or less, absorption in the long wavelength region does not become too large, and the internal transmittance spectrum in the visible light region can be flattened, which may cause uneven brightness or uneven color in the plane. Absent. The amount of divalent iron is more preferably 10 mass ppm or less, further preferably 5 mass ppm or less, particularly preferably 2.5 mass ppm or less. From the viewpoint of flattening the internal transmittance spectrum in the visible light region, the lower the amount of divalent iron, the better. However, if it is 0.1 mass ppm or more, the solubility of glass can be improved, and the visible light region can be improved. It is more preferable because the internal transmittance spectrum in can be flattened more. The amount of divalent iron is more preferably 0.5 mass ppm or more, particularly preferably 1 mass ppm or more.

The amount of divalent iron can be adjusted by the amount of the oxidizing agent added during glass production. Here, the total iron oxide amount can be measured by fluorescent X-ray measurement, and the divalent iron amount can be measured according to ASTM C169-92. Incidentally, divalent iron content measured was expressed in terms of Fe ₂ O _3.

The glass according to the present invention preferably has an average internal transmittance in the visible light region at a length of 50 mm of 97% or more, more preferably 98% or more, and further preferably 99% or more. Here, the visible light region is a range of wavelength 380 to 780 nm.

The glass according to the present invention may be a flat plate. The present invention will be described below by taking this glass plate as an example. The plate thickness of the glass plate is preferably 1.0 mm to 3.0 mm. When the plate thickness is 3.0 mm or less, the weight and the thickness can be set within appropriate ranges when used in a liquid crystal display device. The plate thickness of the glass plate is more preferably 2.5 mm or less, further preferably 2.0 mm or less.

When the plate thickness of the glass plate is 1.0 mm or more, the glass plate has appropriate rigidity, and the self-supporting property of the glass alone can be secured. When the plate thickness is 1.0 mm or more, the glass plate thickness is equal to or more than the width of a light source that is normally used when used in an edge light type planar light emitting device, and therefore, the light is emitted from the glass plate. The light can be efficiently received. The plate thickness of the glass plate is preferably substantially uniform.

The alkaline earth metal deficient layer in the glass plate according to the present invention preferably has an arithmetic average roughness Ra of the surface of 0.5 to 10 nm. The arithmetic mean roughness Ra of the surface of the alkaline earth metal deficient layer is more preferably 5 nm or less, further preferably 2 nm or less, and particularly preferably 1 nm or less.

As described above, one of the causes of clouding on the surface of the light guide plate placed under high temperature and high humidity for a long time is that the organic substances attached to the glass surface are alkaline earth metal components on the glass surface, and alkali metal components. The reaction is to form a salt. Organic substances are derived from constituent members of displays and backlights, and it is difficult to completely eliminate their existence. Therefore, the glass plate according to the present invention is provided with an alkaline earth metal deficient layer for the purpose of preventing the reaction with the alkaline component on the glass surface to form a salt even if the organic matter is attached.

When the arithmetic average roughness Ra of the surface of the alkaline earth metal deficient layer is 0.5 nm or more, it is difficult for organic substances to adhere to the surface of the alkaline earth metal deficient layer, and even if a small amount adheres, it is difficult for the organic matter to spread, and the glass surface The probability of contact with the alkaline earth metal component and the alkali metal component decreases. As a result, it is possible to suppress the occurrence of clouding on the surface of the light guide plate even when it is placed under high temperature and high humidity for a long time.

On the other hand, when the arithmetic mean roughness Ra of the surface of the alkaline earth metal deficient layer is 10 nm or less, the optical characteristics of the light guide plate are not affected, and the brightness reduction and the brightness unevenness of the planar lighting device using the light guide plate are not affected. Is less likely to occur.

[Glass plate manufacturing method]
The glass plate according to the present invention can be manufactured by preparing the raw materials so that the composition of the glass to be obtained will be a predetermined composition, and melt-molding by a usual method. Examples of the molding method include a float method and a fusion method.

When molding by the float method, there is a bottom surface that comes into contact with molten metal (for example, molten tin) during molding, and a top surface that faces the bottom surface. The molten metal enters the bottom surface in contact with the molten metal at the time of molding, so that the concentration of the metal becomes higher than that of the top surface and the inside of the glass plate. In the float method, since molten tin is used as the molten metal, the bottom surface has a higher tin concentration than the top surface and the inside of the glass plate. After the molding, the main surface and the end surface are subjected to surface treatment such as polishing to obtain desired shape characteristics.

The method for producing a glass plate according to the present invention is characterized by including a step of subjecting the glass having the above composition to a dealkalizing earth metal treatment with an acid gas or an acid liquid.

Examples of the acidic gas include at least one acidic gas selected from SO ₂ gas, SO ₃ gas, HCl gas and HF gas, or a mixed gas containing at least one acidic gas selected from these. Examples of the acidic liquid include sulfuric acid, hydrochloric acid, and acidic liquids containing these salts.

Specifically, for example, when molding the glass plate of the present invention by the float method, alkaline earth metal by treating the surface layer of the top surface facing the bottom surface, which is the surface in contact with the molten metal during molding, with an acid gas. A depletion layer can be formed. When the glass plate is formed by the float method, the treatment with the acid gas may be online or offline.

As described above, the concentration of the alkaline earth metal oxide is generally low on the bottom surface due to the diffusion of the alkaline earth metal into the molten metal. Therefore, white clouding is less likely to occur on the bottom surface than on the top surface due to the reaction between the alkaline earth metal and the organic matter. Therefore, the weather resistance is improved by forming the alkaline earth metal deficient layer on the top surface. It is less necessary to form an alkaline earth metal deficient layer on the bottom surface as compared with the top surface, but weather resistance is further improved by forming an alkaline earth metal deficient layer on both the top surface and the bottom surface. ..

The temperature of the glass plate in which the acidic gas is brought into contact with the surface layer of the glass plate is preferably in the range of glass transition point +300 to glass transition point -100°C, and in the range of glass transition point +100 to glass transition point -100°C. Is more preferable, and it is further preferable that the glass transition point is within the range of +50 to −50° C. By treating in the vicinity of the glass transition temperature, the dealkaline earth metal reaction can be promoted, re-diffusion from the inside of the glass can be suppressed, and weather resistance can be improved.

The contact time for bringing the acidic gas into contact with the surface layer of the glass plate is not particularly limited, but for example, 2 seconds or more to 300 seconds is preferable, and 5 to 60 seconds is more preferable. If the contact time is too long, the acidic gas promotes the formation of irregular shapes on the surface of the glass plate, the function as a light guide plate becomes insufficient, and it may be difficult to improve the weather resistance. On the other hand, if the contact time is too short, the dealkalizing earth metal reaction with acid gas may become insufficient.

[Light guide plate]
Hereinafter, a light guide plate made of a glass plate according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing one structural example of the light guide plate of the present invention. A light guide plate 10A shown in FIG. 1 has an alkaline earth metal deficient layer 30 on at least one main surface 21 of a glass plate 20, and a dot-shaped light scattering portion 40 on the other main surface 22.

In the light guide plate 10A shown in FIG. 1, the main surface 21 of the glass plate 20 on which the alkaline earth metal deficient layer 30 is formed is a light emitting surface, and the main surface 22 of the glass plate 20 on which the light scattering section 40 is provided. Is the light scattering surface.

FIG. 2 is a schematic cross-sectional view showing another configuration example of the light guide plate of the present invention. The light guide plate 10B shown in FIG. 2 includes an alkaline earth metal deficient layer 31 on the main surface 21 of the glass plate 20. A dot-shaped light scattering portion 40 is provided on one barrier layer 32.

In the light guide plate 10B shown in FIG. 2, the main surface 21 of the glass plate 20 on the side not provided with the light scattering portion 40 is a light emitting surface, and the main surface 22 of the glass plate 20 on the side provided with the light scattering portion 40 is light scattering. Is a face. In the light guide plates 10A and 10B of the present invention, the dot-shaped light-scattering portion 40 has an arbitrary configuration and may not be provided.

In the case where the light guide plate 10B shown in FIG. 2 does not include the light scattering portion 40, either of the main surfaces 21 and 22 of the glass plate 20 may be the light emitting surface (light scattering surface).

In the light guide plate 10A shown in FIG. 1, the main surface 21 of the glass plate 20 on the side where the alkaline earth metal deficient layer 30 is formed is the light emitting surface, and the main surface 22 of the glass plate 20 on the side having the light scattering portion 40. Is the light scattering surface. In the light guide plate 10B shown in FIG. 2, the main surface 21 of the glass plate 20 on the side not provided with the light scattering portion 40 is the light emitting surface, and the main surface 22 of the glass plate 20 on the side provided with the light scattering portion 40 is It is a light scattering surface. In terms of improving the light extraction efficiency, as in the light guide plate 10A shown in FIG. 1, the dot-shaped light scattering portion 40 is directly formed on the bottom surface to form a light scattering surface, and the top surface is deficient in alkaline earth metal. It is preferable to provide the layer 30 as a light emitting surface.

The dot-shaped light scattering portion 40 is composed of a plurality of dots and disturbs the propagation direction of light propagating inside the light guide plates 10A and 10B (in the case of the light guide plates 10A and 10B of FIGS. 1 and 2). , To be provided on the main surface 21) of the glass plate 20. The dot-shaped light-scattering portion 40 scatters light on the light-scattering surface side surfaces of the light guide plates 10A and 10B (in the case of the light guide plates 10A and 10B of FIGS. 1 and 2, the main surface 22 of the glass plate 20) as an example. The paint can be formed by a known method such as screen printing or inkjet printing.

Examples of the shape of the dot include a circle, an ellipse, a rectangle, a triangle, a polygon, and the like. However, it is possible to disturb the propagation direction of the light propagating inside the light guide plates 10A and 10B and guide it to the light exit surface. There is no particular limitation as long as it can. The shape, size, etc. of the dots can be changed for each part of the light reflecting surface as required.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. The “depth” on the horizontal axis in the graphs of FIGS. 3 to 11 means the distance in the direction from the top surface of the outermost surface of the glass plate to the bottom surface.

Example 1
[Fabrication of glass plate]
A glass material, which was molded on a molten metal by the float method and was prepared to have the following composition, was melted, and the glass material melted on the molten tin in the float bath was molded into a glass ribbon. In Example 1, in the layering process of the glass plate manufacturing line (online) with respect to the top surface of the glass ribbon, SO ₂ and SO ₃ gases which are acidic gases (total concentration is about 10%, the balance other than the active ingredient is It was all air.) The temperature of the glass plate at the time of contact with the acidic gas is 500° C., the acidic contact time is about 30 seconds, and the flow rate of the acidic gas at the time of spraying is 0.5 Nm ³ /hr in total of SO ₃ and SO ₂ . The glass ribbon obtained was cut to prepare the glass plate of Example 1.

Composition of glass plate of Example 1 (portion other than alkaline earth metal deficient layer):
In the mass percentage display of the oxide standard,
SiO ₂ 64.2%
Al ₂ O ₃ 7.4%
CaO 4%
SrO 3.3%
BaO 8%
Na ₂ O 13.2%
A composition containing.

[Evaluation of glass plate]
The alkaline earth metal element content in the glass plate of this example was measured in the direction from the top surface to the bottom surface of the glass plate under the following XPS measurement conditions.

(XPS measurement conditions)
The depth direction distribution of each element concentration in the cleaned glass substrate was measured by X-ray photoelectron spectroscopy using C60 ion sputtering (hereinafter referred to as XPS). For the measurement, ESCA5500 manufactured by ULVAC-PHI, Inc. was used, and Si(2p), Al(2p), Na(2s), Ca(2s), Sr(3p3), Ba(3d5), O(1s) were used. Using the peak, the measurement was performed under the conditions of a pass energy of 117.4 eV, an energy step of 0.5 eV/step, and a detection angle (angle between the sample surface and the detector) of 75°. The analysis software MultiPak was used for the spectrum analysis. The Shirley method was applied to the subtraction of the spectral background.

The measurement results are shown in Table 1 below and FIGS. 3 and 8.

As shown in Table 1 and FIG. 3, the content of each of the alkaline earth metal elements Ca, Sr, and Ba in the region within a depth of 5 nm from the surface layer is 1 mass% or less, and the alkaline earth metal is The existence of a depletion layer was confirmed.

Comparative Example 1
Example 1 was repeated except that the spraying treatment with an acidic gas was not performed in [Production of glass plate] of Example 1.

[Evaluation of glass plate]
Under the same XPS measurement conditions as in Example 1, the alkaline earth metal element content in the glass plate of this comparative example was measured in the direction from the top surface to the bottom surface of the glass plate.

The measurement results are shown in Table 2 below and FIGS. 6 and 11.

As shown in Table 2 and FIG. 4, in [Production of Glass Plate], the glass plate of Comparative Example 1 in which the spraying treatment with the acidic gas was not performed did not have an alkaline earth metal deficient layer. From this result, it was found that the alkaline earth metal deficient layer was formed by subjecting the glass satisfying the composition range in the present invention to the spray treatment with the acidic gas.

Comparative example 2
A glass plate was prepared under the same conditions as in Example 1 except that the following composition was adopted.

Composition of glass plate of Comparative Example 2:
In the mass percentage display of the oxide standard,
SiO ₂ 72.8%
Al ₂ O ₃ 0.9%
CaO 7.7%
MgO 4.8%
Na ₂ O 13.3%
K ₂ O 0.2%
A composition containing.

[Evaluation of glass plate]
Under the same XPS measurement conditions as in Example 1, in the direction from the top surface to the bottom surface of the glass plate, the glass plate of this comparative example has an alkaline earth metal deficient layer having an alkaline earth metal content of 1% by mass or less. Whether or not it was measured.

The measurement results are shown in Table 3 below and FIG. 7.

As shown in Table 3 and FIG. 7, in the glass plate of Comparative Example 2, no alkaline earth metal deficient layer was confirmed.

(Weather resistance test)
The glass plate obtained in each Example and each Comparative Example was left to stand under high temperature and high humidity conditions of 60° C. and 90% RH for 1000 hours, and the degree of cloudiness of the glass plate was visually evaluated.
The evaluation criteria are as follows.
○: No cloudiness occurred ×: Cloudiness occurred

The results are shown below.
Glass plate of Example 1: ○
Glass plate of Comparative Example 1: ×
Glass plate of Comparative Example 2: x
The glass plates of Example 1 and Comparative Example 1 each had an average internal transmittance in the visible light region of 50 mm length of 98.8%. When the internal transmittance is T _in , the internal transmittance T _in means a certain optical path length L (cm), an incident light intensity I ₀ (%), and a certain optical path length L (cm) after being transmitted. When the intensity of light is I ₁ (%) and the attenuation rate of light due to reflection is R (%), the value can be represented by the following formula.
logT _in =(log(I ₁ /I ₀ )−logR)

As described above, whilst the glass plates of Comparative Example 1 and Comparative Example 2 were clouded white, the glass plate of Example 1 was not clouded white. From this result, it was found that the glass plate of the present invention has an excellent transmittance suitable for a light guide plate, and can suppress the occurrence of cloudiness on the surface of the glass even when it is placed under high temperature and high humidity for a long time. ..

10A, 10B: Light guide plate 20: Glass plate 21, 22: Main surface 30, 31: Alkaline earth metal deficient layer 32: Barrier layer 40: Light scattering part

Claims (8)

A glass having the following composition, in which at least one of the main surfaces has an alkaline earth metal element content of 1% by mass or less by XPS measurement in a region within a depth of 5 nm from the surface layer.
The oxide-based mass percentage display is 60 to 85% SiO ₂ , 0 to 10% Al ₂ O ₃ , 0 to 10% MgO, 0 to 20% CaO, 0 to 15% SrO, and BaO. Composition containing 0 to 15%, ₂ to 20% Na ₂ O, 0 to 10% K ₂ O, and 0 to 20% B ₂ O ₃ . The glass according to claim 1, wherein the content of the alkaline earth metal element in a region within a depth of 10 nm from the surface layer on at least one main surface is 4% by mass or less in each case by XPS measurement. The glass according to claim 1 or 2, wherein at least one of the main surfaces has an alkaline earth metal element content of 5.5 mass% or less in an area within a depth of 15 nm from the surface layer as measured by XPS measurement. The glass has a bottom surface in contact with a molten metal at the time of molding, and a top surface facing the bottom surface, and an XPS measurement of an alkaline earth metal element in a region within a depth of 5 nm from the surface layer on the top surface. The glass according to any one of claims 1 to 3, wherein each content is 1% by mass or less. The glass according to any one of claims 1 to 4, which has a plate thickness of 1.0 to 3.0 mm. A glass light guide plate made of the glass according to claim 1. On one main surface of the glass according to any one of claims 1 to 5, each content of the alkaline earth metal elements in a region within a depth of 5 nm from the surface layer by XPS measurement is 1% by mass or less. The glass light guide plate according to claim 6, further comprising a dot-shaped light-scattering portion on the other main surface. A method for producing glass, which comprises a step of subjecting at least one main surface of glass having the following composition to dealkali earth metal treatment with an acid gas or an acid liquid.
By mass percentage based on oxides, _{SiO 2 60~85%, Al 2 O} 3 0-10% of MgO 0-10%, 0 to 20% of CaO, 0 to 15% of SrO, BaO, Composition containing 0 to 15%, ₂ to 20% Na ₂ O, 0 to 10% K ₂ O, and 0 to 20% B ₂ O _3.

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